The present invention relates to a tool exchanger for boring mills of the type having a spindle carriage horizontally slidable on a support which is either solid with the frame or part of a movable console on a frame which can itself be moved along the axis of the spindle of the carriage or perpendicular to this axis.
From French Pat. No. 1,236,668 in particular, it is well known to extract and insert machine tools from a tool magazine in which the tools are disposed horizontally and parallel to the axis of a spindle by use of a rotary pincer-arm which permits exchange between the tool mounted on the spindle and a tool disposed in the magazine by combining motions of 180.degree. rotation and translation. In other machines, the magazine is disposed perpendicularly to the axis of the spindle and the axis of the pincer-arm is situated 45.degree. from both the axis of the spindle and the axis of the magazine.
In practice, however, the solutions adopted either do not respond suitably to all types of machines, or have substantial drawbacks.
Thus, in the case of machines having sliding spindle carriages, the installation of the magazine on the carriage leads to variable loads on the carriage which interferes with the working precision of the machine.
Accordingly, it is an object of the present invention to embody a tool exchanger in which the magazine is not borne by the sliding carriage.
Also, in many tool exchange devices, the interference of their operation with the motion of moving parts such as table, console (bracket) or carriage requires limiting these movements. This requires reduction of the size of the pieces that can be worked on the machine, and reduction of the size of the tools that can be used.
Accordingly, it is another object of the present invention to provide a tool exchange apparatus which does not set such limitations on the table, console or carriage movement, or on the length of the tools that can be used and which is completely clear of the active parts of the machine during the idle position.
Another drawback of certain prior devices is that they prevent or diminish access to the machine. Accordingly, it is another object of the present invention to provide an apparatus which does not entrain an appreciable diminution in frontal or lateral access to the machine by the operators who are to use it.
In certain machines the magazine is situated above the machine at a height which is inaccessible or difficult for operators to reach. This constitutes a serious drawback, and the present invention envisages the embodiment of a device in which the magazine is easily accessible.
The magazine is conventionally placed above the machine to avoid interference of the path of the pincer-arm with the paths of the other members, or with the movements of the headstock or spindle-holding head, or with the guides of the sliding carriage. This problem is sometimes solved by having the pincer-arm withdraw tools from a position above the spindle. This leads to situating the magazine at some height.
Accordingly, it is another object of the present invention to provide an apparatus capable of withdrawing tools, and installing them on the spindle from above without having the magazine placed in a position that is inaccessible.
In many tool exchangers, the pincer-arm simultaneously withdraws a tool from the magazine and from the spindle and exchanges them in a 180.degree. rotation. As a result, the withdrawn tool is arranged in the magazine, not in a specific location, but in the position in the magazine from which the fresh tool was taken. This means that programming of tool changes is much more complicated since the tools do not have established places in the magazine. In particular, if the same tool is to be used several times in the course of consecutive operations, marking of the position in the magazine where it is placed raises problems.
In the tool exchanger of the present invention this problem is solved since a given tool can easily be replaced in a given position on the magazine.
The use of pincer-arms which effect tool exchange by a simple 180.degree. rotation with the pincer-arm simultaneously displacing the extracted tool and the tool to be installed requires a relatively low density of tools in the magazine. Such pincer-arms carry lateral pincers whose path sweeps a wide area, and it is necessary, therefore, to provide a certain minimum spacing between the tools in the magazine. However, the tool exchanger of the present invention lacks this drawback.
Furthermore, an important requirement is saving time during the tool exchange. In many machines, the tool exchange cannot take place until the headstock or spindle-bearing head is in a given position. The time required to bring the spindle to the appropriate position represents an expenditure of time. In addition, time is required for the successive rotation and translation of the pincer-arm.
Accordingly, it is another object of the present invention to provide an apparatus wherein the pincer-arm can execute a series of preparatory composite movements while the machine is still in operation so as to considerably reduce the time necessary for the tool exchange.